Keep alive message overhead reduction for communication networks

ABSTRACT

A method of communications in a network having plurality of nodes including a base node (BN) and a plurality of levels (i) each including at least one service node (SN). The number (Ni(t)) of SNs registered in each of a plurality of i are determined. The current Keep Alive timer out (KA_TO) value for a KA timer at the BN is dynamically adjusted to an updated KA_TO value based on Ni(t) and i. Dynamically adjusting KA_TO values reduces the KA message overhead the network compared to known KA_TO value implementations.

CROSS REFERENCE TO RELATED APPLICATIONS

This application and the subject matter disclosed herein claims thebenefit of Provisional Application Ser. No. 61/592,346 entitled “DataConcentrator Regulated Keep-Alive Traffic Adaptation in PRIME” filedJan. 30, 2012, which is herein incorporated by reference in itsentirety.

FIELD

Disclosed embodiments relate generally to the field of communications,and, more specifically, methods of node availability in communicationnetworks.

BACKGROUND

Smart grid technology refers to ongoing improvements for thetransmission and distribution of electricity from points of generationto consumers. A key component in a smart grid network is the so-called“smart-metering” network. In a typical smart-metering network,electricity (or other utility) meters located at a residency or otheredifice are able to transmit the real-time meter readings throughpowerlines back to the power concentrators and provide valuablereal-time electricity control and billing information for theelectricity provider.

Due to power efficiency considerations and severe noise in powerlines,direct transmission of metering information through powerlines haslimited scopes. Therefore, a typical smart metering network has atree-like topology, including: 1) a data concentrator that serves as theroot node in the tree (also called a base node, BN); 2) metering devicesat terminal nodes (TNs) in the tree which send their metering readingsback to the BN; and 3) switching nodes (SWs) which act as the branchnodes in the tree. The SWs relay the data traffic to the further hopsfor communication pairs (e.g., a TN and a BN) beyond their directcommunication reach. The SWs and TNs in the network are collectivelyreferred to herein as service nodes (SNs).

Powerline-Related Intelligent Metering Evolution (PRIME) is a Europeanstandard of smart-metering network. The PRIME standard defines lowerlayers of a powerline communication narrowband data transmission systemfor the electric power grid using Orthogonal Frequency-DivisionMultiplexing (OFDM) in the 42 to 90 kHz band. A PRIME network utilizes atree-like topology as described above. In a PRIME network, the MediaAccess Control (MAC) function enables the BN, as well as the SWs to sendout beacons periodically. The beacons also help all the SNs in thenetwork synchronize their clocks and virtually chop the time domain intodiscrete time frames.

A Keep Alive (KA) procedure is used to detect whether the BN and SNs arealive. Conventional KA procedures require the BN to periodically send aKA request to every SN that is part of the network, and await a KAresponse from the SNs. KA frames allows the BN to detect when a SNbecomes unreachable due to changes in network configuration/topology(bad link, channel conditions, load variations, SN leaving thesubnetwork, etc.), or fatal errors at the SN it cannot recover from. TheKA procedure is performed using timing (e.g., a particular fixed KAtimeout value used) which is without regard to the number of registeredSNs and their levels (depth) in the network.

FIG. 1 illustrates a powerline communications network 100 comprising aBN 110, SNs comprising as SN1-SN5, and SWs comprising SW1-SW4. Network100 has 3 levels shown as Level 1, Level 2, and Level 3. FIG. 1 showstransmission of KA request frames by the BN 110 (ALV_B frames) forclarity to only SW1, SW2 and TN1 and the response frames from these SNs(ALV_S frames). Although the KA frames are beneficial for allowing theBN 110 to detect the connectivity of the respective SNs in the network100, KA frames introduce additional traffic overhead in the network. Itis noted that both the ALV_B and ALV_S messages are transmitted in anunicast fashion to each SN in the network 100 which further adds tonetwork overhead.

SUMMARY

Disclosed embodiments are directed, in general, to communicationnetworks and, more specifically, to methods, modems and communicationdevices which implement Keep Alive (KA) message overhead reduction.Disclosed KA message overhead reduction algorithms regulate the numberof KA messages in the network by dynamically setting the KA timeout(KA_TO) value for the KA timer at the base node (BN) based on number ofregistered service nodes (SNs) and their levels (depth) in the network.The updated KA_TO value is then communicated by the BN to the SNs in thenetwork, such as by using an ALV_B frame for a powerline communicationsnetwork based on the PRIME standard.

KA_TO values are dynamically adjusted based on the number of SNsregistered in each of the plurality of levels in the network (i), with aSN weighting that can increase as the level number increases. DisclosedKA_TO value adjustments also allow the BN to become cognizant of SNconnectivity failures within a reasonable time.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, wherein:

FIG. 1 illustrates a powerline communications network showing thetransmission of KA frames by the BN (ALV_B) to some of the SNs in thenetwork and responses received from these SNs (ALV_S).

FIG. 2 is a flowchart for an example KA message overhead reductionalgorithm, according to an example embodiment.

FIG. 3 shows a communication device having a disclosed modem thatimplements a disclosed KA message overhead reduction algorithm,according to an example embodiment.

DETAILED DESCRIPTION

Disclosed embodiments now will be described more fully hereinafter withreference to the accompanying drawings. Such embodiments may, however,be embodied in many different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of this disclosure to those having ordinaryskill in the art. One having ordinary skill in the art may be able touse the various disclosed embodiments and there equivalents. As usedherein, the term “couple” or “couples”, unless clarified, such as in“communicably coupled”, is intended to mean either an indirect or directelectrical connection. Thus, if a first device couples to a seconddevice, that connection may be through a direct electrical connection,or through an indirect electrical connection via other devices andconnections.

FIG. 2 is a flowchart for an example method 200 of KA message overheadreduction in a communications network, according to an exampleembodiment. The communications network can be a wired network, such as apowerline communications network, or a wireless communications network.The network has plurality of nodes including a BN and a plurality oflevels (i) each including at least one SN. In step 201 the number(Ni(t)) of SNs registered in each of a plurality of i is determined.Step 202 comprises dynamically adjusting a current KA_TO value for a KAtimer at the BN to an updated KA_TO value based on Ni(t) and i. In oneembodiment a sum over i of a product of Ni(t) and i (ΣNi(t)*i) iscomputed and this sum of products ΣNi(t)*i is then compared to at leastone predetermined threshold (Th) value to determine the updated KA_TOvalue. A minimum KA_TO value that is greater than the above sum ofproducts is generally used.

The at least one Th value can comprise a plurality of Th values whichare configured to form a plurality of Th value ranges, with each Thvalue range corresponding to a different candidate KA_TO value, whereinhigher ones of the Th value ranges correspond to higher candidate KA_TOvalues. The Th values can be determined as a candidate KA_TO value*K,where 0<K<1. The minimum KA_TO value can be calculated from satisfyingthe equation ΣNi(t)*i≦Th (KA_TO*K), where 0<K<1 can be used.

The SNs in the network also each have a KA timer. Step 203 comprisescommunicating the updated KA_TO value to the SNs. For example, in apowerline communications network utilizing the PRIME standard, theupdated KA_TO value can be sent to the SNs in an ALV.TIME field withinan ALV_B frame. The network can utilize Orthogonal Frequency-DivisionMultiplexing (OFDM) signaling, or signaling based on other modulationtechniques.

Implementations of disclosed KA algorithms can involve BN′ transmissionof KA requests (ALV_B) to SNs in the network up to a certain number oftimes prior to the KA_TO expiry. In one particular implementation, theBN attempts up to a fixed number (e.g., 3) times to get a response froma particular SN in the network. By dynamically adapting the currentKA_TO value based on the registered node arrangement, the overall KAtraffic in the network can be reduced while still detecting a connectionloss in reasonable time. One particular example disclosed KA messageoverhead reduction algorithm is configured as follows:

-   i) A minimum KA_TO value and a maximum KA_TO value is provided, such    as 32 sec and 4096 sec, respectively, in one particular embodiment;-   ii) An initial KA_TO value is set, such as to the minimum KA_TO    value of 32 sec, and ALV_B messages are sent by the BN to the SNs at    16 sec, and retries at 24 sec, 28 sec if needed (i.e. if an ALV_S is    not received);-   iii) The KA_TO value for the KA timer at the BN is dynamically    adjusted as follows. The number of registered SNs in the network at    any given time is maintained by the BN by the nodes registering with    the BN and the BN repeatedly checking if each of the SNs are still    connected by the use of KA messaging (ALV_B messaging), where the    network has i levels with N_(i) SNs at each level i. For example, in    the network 100 shown in FIG. 1 which has 3 Levels, i=3 and assuming    all the nodes shown are registered at a given time ΣNi*i from i=1 to    i=3 is computed as 3(1)+3(2)+3(3)=18. If the sum of the product    (ΣNi*i) exceeds a certain predetermined threshold value, Th_(i),    then the KA_TO value for the KA timer at the BN is dynamically    adjusted upward from its initial KA_TO value assumed in this    particular example to be 32 sec as shown below to up to a maximum    value shown as 4096 sec.    ΣNi*i<Th1:KA_TO=32 sec    Th1<=ΣNi*i<Th2:KA_TO=64 sec    Th2<=ΣNi*i<Th3:KA_TO=128 sec    Th3<=ΣNi*i<Th4:KA_TO=256 sec    Th4<=ΣNi*i<Th5:KA_TO=512 sec    Th5<=ΣNi*i<Th6:KA_TO=1024 sec    Th6<=ΣNi*i<Th7:KA_TO=2048 sec    ΣNi*i>=Th7:KA_TO=4096 sec

It can be seen that the KA_TO value for updating the BN's Keep-Alivetimer increases when ΣNi*i increases, provided the current KA_TO valueis not already at its maximum allowed value (shown above as 4096 sec).Similarly, when ΣNi*i drops below a certain threshold, the KA_TO valuecan be adjusted downward (assuming the current KA_TO value is above theminimum value, shown as 32 sec) using the same table shown above. Thevalue of the threshold parameters (Th_(i)) can be left to the specificimplementation. This way, the BN can regulate the total KA messagetraffic in the network, while still maintaining the ability to know theconnectivity (registered or non-registered status) of each SN in thenetwork.

Advantages of disclosed KA message overhead reduction algorithmsinclude:

-   1. for powerline implementations, being fully PRIME standard    compliant, and backward compatible with existing implementations;-   2. Simple and easy to implement, generally depending only on a KA_TO    value adjustment to reduce the overall network traffic, and-   3. Efficient as they reduce the overall network overhead associated    with KA messages without compromising the ability to know the    connectivity of all SNs in the network.

FIG. 3 shows a block diagram schematic of a communications device 300comprising a modem 304 including a processor (e.g., a digital signalprocessor, (DSP)) 304 a having associated memory 305 comprisingnon-transitory machine readable storage that implements a disclosed KAloss reduction algorithm at a BN within a communications network,according to an example embodiment. The KA timer is shown as 307. Themodem 304 is shown formed on an integrated circuit (IC) 320 comprising asubstrate 325 having a semiconductor surface 326, such as a siliconsurface. In another embodiment the modem 304 is implemented using 2processor chips, such as 2 DSP chips. As described above, for powerlinecommunication applications, the KA loss reduction algorithm usesinformation regarding the registered SNs in the powerline communicationsnetwork to dynamically adjust the KA_TO value used by the KA timer 307.

Communications device 300 also includes an analog from end (AFE) shownas a transceiver (TX/RX) 306 that allows coupling of the communicationsdevice 300 to the communications media 340, such as a powerline forpowerline communications or the air for wireless communications, tofacilitate communications with SNs in the network. For wirelessapplications, transceiver 306 comprises a wireless transceiver that iscoupled to an antenna (not shown). In one embodiment the transceiver 306comprises an IC separate from IC 320. Besides the DSP noted above, theprocessor 304 a can comprise a desktop computer, laptop computer,cellular phone, smart phone, or an application specific integratedcircuit (ASIC).

EXAMPLES

Disclosed embodiments are further illustrated by the following specificExamples, which should not be construed as limiting the scope or contentof this Disclosure in any way.

Table 1 below shows KA_TO values dynamically selected based on adisclosed KA_TMO algorithm for various network arrangements for a4-level network using K=1/6. Each row in the table corresponds to adifferent time, where node registration and deregistration happens overtime interval shown in levels 2, 3 and 4.

Number of Number of Number of Number of nodes in nodes in nodes in nodesin KA_TO level 1 level 2 level 3 level 4 value 2 2 2 2 128 2 3 2 2 256 23 2 3 256 2 3 1 3 128

The current KA_TO value can be seen to increase from 128 seconds to 256seconds, and then decrease to 128 seconds again based on the currentregistered network arrangement. Disclosed adjustment to the KA_TO valuebased on the current node arrangement reduces the overall KA trafficcompared to conventional KA algorithms, while still being able to detecta connection loss in reasonable time.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this Disclosure pertains havingthe benefit of the teachings presented in the foregoing descriptions,and the associated drawings. Therefore, it is to be understood thatembodiments of the invention are not to be limited to the specificembodiments disclosed. Although specific terms are employed herein, theyare used in a generic and descriptive sense only and not for purposes oflimitation.

We claim:
 1. A method of communications in a network having plurality ofnodes including a base node (BN) and a plurality of levels (i) eachincluding at least one service node (SN), comprising: determining anumber (Ni(t)) of said SNs registered in each of said plurality of i,and dynamically adjusting a current Keep Alive time out (KA_TO) valuefor a KA timer at said BN to an updated KA_TO value based on said Ni(t)and said i.
 2. The method of claim 1, wherein said BN transmits KArequests in an ALV_B frame to said SNs up to a predetermined number oftimes prior to an expiry of said updated KA_TO value.
 3. The method ofclaim 2, further comprising said BN communicating said updated KA_TOvalue to said SNs in an ALV.TIME field within said ALV_B frame.
 4. Themethod of claim 1, further comprising: computing a sum over said i of aproduct of said Ni(t) and i (ΣNi(t)*i) and comparing said ΣNi(t)*i to atleast one predetermined threshold (Th) value to determine said updatedKA_TO value.
 5. The method of claim 4, wherein said at least one Thvalue comprises a plurality of said Th values which are configured toform a plurality of Th value ranges, with each said Th value rangecorresponding to a different candidate KA_TO value, and wherein higherones of said Th value ranges correspond to higher candidate KA_TOvalues.
 6. The method of claim 5, wherein said predetermined threshold(Th) values are determined as: said candidate KA_TO value*K, where0<K<1.
 7. The method of claim 1, wherein said network utilizesOrthogonal Frequency-Division Multiplexing (OFDM) signaling.
 8. Themethod of claim 1, wherein said communications comprise powerlinecommunications.
 9. The method of claim 1, wherein said communicationscomprise wireless communications.
 10. A modem, comprising: a processor;a memory comprising non-transitory machine readable storage, whereinsaid processor is communicably coupled to access data stored in saidmemory, wherein said memory stores a Keep Alive (KA) message overheadreduction algorithm and said processor is programmed to implement saidKA message overhead algorithm, said KA message overhead algorithm:generating at least one parameter from data including a number (Ni(t))of service nodes (SNs) registered in each of a plurality of levels (i)for a communications network having a base node (BN), said BN includinga KA timer having a current KA_TO value, and dynamically calculating anupdated KA_TO value for said KA timer based on said Ni(t) and said i.11. The modem of claim 10, wherein said modem is formed on an integratedcircuit (IC) comprising a substrate having a semiconductor surface, andwherein said processor comprises a digital signal processor (DSP). 12.The modem of claim 10, wherein said KA message overhead algorithmfurther implements: computing a sum over said i of a product of saidNi(t) and i (ΣNi(t)*i) and comparing said ΣNi(t)*i to at least onepredetermined threshold (Th) value to determine said updated KA_TOvalue.
 13. The modem of claim 12, wherein said at least one Th valuecomprises a plurality of said Th values which are configured to form aplurality of Th value ranges, with each said Th value rangecorresponding to a different candidate KA_TO value, and wherein higherones of said Th value ranges correspond to higher candidate KA_TOvalues.
 14. A communications device, comprising: a modem, comprising: aprocessor; a memory comprising non-transitory machine readable storage,wherein said processor is communicably coupled to access data stored insaid memory, wherein said memory stores a Keep Alive (KA) messageoverhead reduction algorithm and said processor is programmed toimplement said KA message overhead algorithm, said KA message overheadalgorithm: generating at least one parameter from data including anumber (Ni(t)) of service nodes (SNs) registered in each of a pluralityof levels (i) for a communications network having a base node (BN), saidBN including a KA timer having a current KA_TO value, and dynamicallycalculating an updated KA_TO value for said KA timer based on said Ni(t)and said i, and a transceiver communicably coupled to said modem. 15.The communications device of claim 14, wherein said modem is formed onan integrated circuit (IC) comprising a substrate having a semiconductorsurface, and wherein said processor comprises a digital signal processor(DSP).
 16. The communications device of claim 14, wherein saidtransceiver comprises a powerline transceiver.
 17. The communicationsdevice of claim 14, wherein said transceiver comprises a wirelesstransceiver.
 18. The communications device of claim 14, wherein said KAmessage overhead algorithm further implements: computing a sum over saidi of a product of said Ni(t) and i (ΣNi(t)*i) and comparing saidΣNi(t)*i to at least one predetermined threshold (Th) value to determinesaid updated KA_TO value.
 19. The communications device of claim 18,wherein said at least one Th value comprises a plurality of said Thvalues which are configured to form a plurality of Th value ranges, witheach said Th value range corresponding to a different candidate KA_TOvalue, and wherein higher ones of said Th value ranges correspond tohigher candidate KA_TO values.